Triangle Area Calculator

Q: "How do I find the area of a triangle?"

"Area = ½ × base × height. Or use Heron's formula if you know all three sides."

Q: "What is Heron's formula?"

"If sides are a, b, c and s = (a+b+c)/2, then area = √(s(s−a)(s−b)(s−c))."

Q: "Can I use base and height or three sides?"

"Yes. Choose \"Base and height\" or \"Three sides (Heron)\" and enter the values."

Q: "What units can I use?"

"Any length unit (meters, feet). Area is in square units (m², ft²)."

Q: "Do the three sides have to form a valid triangle?"

"Yes. For Heron's formula, the sum of any two sides must be greater than the third."

Calculate triangle area from base and height, or from three sides (Heron's formula). Example: base 10, height 4 → area 20. Copy result.

The area of a triangle is ½ × base × height when you know the base and the perpendicular height. If you know all three sides, use Heron’s formula: let s = (a+b+c)/2, then area = √(s(s−a)(s−b)(s−c)). Choose base/height or three sides and enter the lengths. The result is in square units. Copy the result or Copy with labels.

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Examples

base 10, height 4 → area 20
sides 3, 4, 5 → area 6 (Heron)
base 8, height 5 → area 20

FAQ

How do I find the area of a triangle?

Area = ½ × base × height. Or use Heron's formula if you know all three sides.

What is Heron's formula?

If sides are a, b, c and s = (a+b+c)/2, then area = √(s(s−a)(s−b)(s−c)).

Can I use base and height or three sides?

Yes. Choose "Base and height" or "Three sides (Heron)" and enter the values.

What units can I use?

Any length unit (meters, feet). Area is in square units (m², ft²).

Do the three sides have to form a valid triangle?

Yes. For Heron's formula, the sum of any two sides must be greater than the third.